DivX is a brand name of products created by DivX, Inc. (formerly DivXNetworks, Inc.), including the DivX Codec which has become popular due to its ability to compress lengthy video segments into small sizes while maintaining relatively high visual quality. The DivX codec uses lossy MPEG-4 Part 2 compression, also known as MPEG-4 ASP, where quality is balanced against file size for utility. It is one of several codecs commonly associated with ripping, where audio and video multimedia are transferred to a hard disk and transcoded. As a result, DivX has been a center of controversy because of its use in the replication and distribution of copyrighted DVDs. Many newer "DivX Certified" DVD players are able to play DivX encoded movies, although the Qpel and GMC features are often omitted to reduce processing requirements. They are also excluded from the base DivX encoding profiles for compatibility reasons.
It can play some Movie files that even WMA can't.
The latest generation, DivX 6, was released on June 15, 2005 and expands the scope of DivX from including just a codec and a player by adding a media container format. This optional new file format introduced with DivX 6 is called "DivX Media Format" ("DMF") (with a .divx extension) that includes support for the following DVD-Video and VOB container like features.
DivX Media Format (DMF) features:
Interactive video menus
Multiple subtitles (XSUB)
Multiple audio tracks
Multiple video streams (for special features like bonus/extra content, just like on DVD-Video movies)
Chapter points
Other metadata (XTAG)
Multiple format
Partial backwards compatibility with AVI
This new "DivX Media Format" also came with a "DivX Ultra Certified" profile, and all 'Ultra' certified players must support all "DivX Media Format" features. While video encoded with the DivX codec is an MPEG-4 video stream, the DivX Media Format is analogous to media container formats such as Apple's QuickTime. In much the same way that media formats such as DVD specify MPEG-2 video as a part of their specification, the DivX Media Format specifies MPEG-4-compatible video as a part of its specification. However, despite the use of the ".divx" extension, this format is an extension to the AVI file format. The methods of including multiple audio and even subtitle tracks involve storing the data in RIFF headers and other such AVI hacks which have been known for quite a while, such that even VirtualDubMod supports them. DivX, Inc. did this on purpose to keep at least partial backwards compatibility with AVI, so that players that do not support the new features available to the .divx container format (like interactive menus, chapter points and XSUB subtitles) they can at least play that primary video stream (usually the main movie if the .divx contain multiple video streams like special features like bonus materials). Of course, the DivX codec and tools like Dr.DivX still support the traditional method of creating standard AVI files.
The main competitors in the proprietary commercial video compression software market are Microsoft's Windows Media Video series, Apple Inc.'s QuickTime, and the RealNetworks RealVideo series.
While DivX has long been renowned for its excellent video quality, its free and open source equivalent Xvid , today offers comparable quality, also based on MPEG-4 Part 2 (MPEG-4 ASP). (Xvid is DivX spelled backwards.) In a series of subjective quality tests at Doom9.org, the DivX codec has been successively beaten by Xvid every year since 2003.[11]
The open source library libavcodec can decode and encode MPEG-4 video that can be encoded and decoded with DivX (and other MPEG-4 codecs, such as Xvid or libavcodec MPEG-4). Combined with image postprocessing code from the MPlayer project, it has been packaged into a DirectShow filter called ffdshow, which can be used for playback with most Windows video players and reportedly achieves higher image quality on playback while generating less CPU load than the DivX decoder.[12]
Since the standardization of H.264/MPEG-4 AVC, also known as MPEG-4 Part 10, a new generation of codecs has arisen, such as x264. Despite being at a relatively early stage of development, these codecs out-performed DivX in Doom9's 2005 quality test, thanks to the more advanced features of MPEG-4 Part 10. Part 10's advanced features come at a cost: they are two to three times more CPU intensive than the relatively lightweight algorithms used in the DivX codec. It remains to be seen whether DivX will release a new codec based on the newer specification, like the Xvid team did with their Xvid AVC codec (not yet released to the public).